A clutch mechanism of the type to which the present invention relates generally consists of a clutch hub and a clutch sleeve. Spring loaded drive members resiliently extend from pockets in the clutch hub to engage with recesses of the clutch sleeve to effect torque transmission between the hub and the sleeve. It is known in the prior art to form the heads of the drive members with wedged engagement heads which are biased outwardly to enter recesses formed on the wall of the clutch sleeve.
Safety clutches operating on the principle of a clutch ratchet are generally known in the art. In the patent of Kunze, U.S. Pat. No. 4,261,453, two embodiments of sleeve recesses are shown in FIGS. 3 and 4, respectively. In one embodiment the side surfaces forming the recesses extend at different angles with respect to a radial plane passing through the intersection of the sides. In such an arrangement, a greater torque can be transmitted in one direction of rotation than in the reverse direction of rotation. In the other embodiment, the recesses into which the drive members seat have uniform side surfaces so that the torque transmitted in each direction is equivalent.
These types of clutches are generally used in agricultural equipment having an auger rotating on an axis perpendicular to the direction of travel of the machine for moving grain or hay into a loading compartment of the implement. From time to time the auger will get hung up by materials being gathered and sometimes hang up will be caused by foreign materials such as baling string or wire getting caught around the auger causing the clutch hub to disengage from the clutch sleeve. One of the simplest ways to eject the clogging material from the auger is to reverse the direction of the clutch hub and thereby reverse the auger. However, the hang up frequently jams the auger to the extent that the force to reverse the rotation needs to be greater than the force which caused the hang up in the beginning.
This disadvantage is not overcome by the prior art. If the recesses of the clutch sleeve have equal limiting angles, then the force exerted on the sleeve to cause slippage in either direction will be equivalent, and therefore, the clutch will tend to slip in the reverse direction as well as the forward direction.
When a clutch sleeve is manufactured to present recesses having different limiting angles of the side surfaces of the recesses, different torques can be applied to the forward and reverse directions of rotation. Generally, these two torque clutch sleeves are designated to have large differences between forward and reverse, because the manufacture of slightly different forward and reverse disengaging forces is difficult to accomplish. Furthermore, clutch sleeves having different torquing properties are not available in many varieties as an off-the-shelf item.
It has been found that avoidance of the above problems can be achieved by using the positive properties of the two different designs together in one clutch sleeve and thereby avoid the disadvantages of the disengaging clutches of the prior art.